Late Jurassic-Early Cretaceous Northern Qaidam Basin, NW China: Implications for the earliest Cretaceous intracontinental tectonism   总被引：4，自引：0，他引：4  

Lei Wu  Ancheng Xiao  Liqun WangZhongyan Shen  Suping ZhouYuanzhong Chen  Liang Wang  Dong LiuJunya Guan 《Cretaceous Research》2011,32(4):552-564

Formation of Mesozoic western China, which was dominated by tectonic amalgamation along its southern margin and associated intracontinental tectonisms, holds a key for interpreting the succedent Cenozoic evolution. This paper presents new data including lithology, sedimentary facies, stratigraphic contact, seismic interpretation and paleo-structures within the Upper Jurassic-Lower Cretaceous strata in the northern Qaidam Basin, NW China. These data all account for a contractional tectonic deformation in the earliest Cretaceous. The South Qilian Shan, according to the sedimentary features and provenance analysis, reactivated and exhumated during the deformation, controlling the deposition of the Lower Cretaceous sequences. A simplified model for the Late Jurassic-Early Cretaceous paleogeography and tectonics of the northern Qaidam Basin is accordingly proposed. The results also support a ∼25° clockwise rotation of the Qaidam Basin since the Early Cretaceous and a more accurate Mesozoic evolution process for the basin. This earliest Cretaceous deformation, associated with the reactivation of the South Qilian Shan at the time, are part of the intracontinental tectonisms in central Asia during the Mesozoic, and probably driven by both the closure of the Mongol-Okhostk Ocean to the north and the collision of the Lhasa and the Qiangtang blocks to the south.  相似文献   

Distribution of continental red paleosols and their forming mechanisms in the Late Cretaceous Yaojia Formation of the Songliao Basin, NE China     

Xuebin Du  Xinong Xie  Yongchao Lu  Jianye Ren  Shun ZhangPenglin Lang  Tao ChengMing Su  Cheng Zhang 《Cretaceous Research》2011,32(2):244-257

  相似文献   

Integrated biostratigraphy and carbon isotope stratigraphy of the Lower Cretaceous (Barremian to Albian) Adriatic-Dinaridic carbonate platform deposits in Istria, Croatia     

Blanka Cvetko Tešovi?  Bosiljka Glumac 《Cretaceous Research》2011,32(3):301-324

The Adriatic-Dinaridic carbonate platform (ADCP) was one of the largest and relatively well preserved Mesozoic platforms in the Mediterranean region (central Tethys). The peninsula Istria, in the northwestern part of the ADCP, is built up predominantly of shallow-water carbonates of the Middle Jurassic (Dogger) to Eocene age and, to a lesser extent, of Paleogene clastic deposits (flysch and calcareous breccia). This study focuses on a Lower Cretaceous (Barremian to Albian) succession of strata at five localities in western Istria. Stratigraphic determinations are based on identification of nine microfossil assemblages (benthic foraminifera and calcareous algae Dasycladales) and on using their taxa as index fossils. The age of strata with these microfossil assemblages, however, is questionable. Most of the age uncertainties are associated with a regional emersion, which occurred on the ADCP during the Aptian or close to the Aptian-Albian transition. It is unclear what portions of the Upper Aptian and/or Lower Albian are missing along this unconformity. A stable isotope study was conducted on homogenous micritic matrix samples in an attempt to resolve some of these uncertainties. Variations in carbon isotope compositions proved useful for stratigraphic correlation between the examined successions of strata, for improving their age determination, and for relating them to other coeval successions that span an important time interval of major oceanographic changes and carbon-cycle perturbations associated with the Early Aptian oceanic anoxic event (OAE 1a).  相似文献   

Large hatchling size in Cretaceous nautiloids persists across the end-Cretaceous mass extinction: New data of Hercoglossidae hatchlings     

Ryoji Wani  Ken’ichi KuriharaKrishnan Ayyasami 《Cretaceous Research》2011,32(5):618-622

The hatchling sizes of the Cretaceous nautiloids (Hercoglossa forbesianus and Cimomia angustus; Hercoglossidae) are reported here for the first time as ranging between 20.4-22.2 mm in diameter. These new data for Hercoglossidae and the previously reported data for Nautilidae and Cymatoceratidae suggest that all Cretaceous nautiloids had large hatchlings irrespective of their taxonomy relative to those in ammonoids. Based on the relationship between hatching events and the nepionic constriction in modern nautili, the hatchling size of nautiloids can be recognized by the constriction on the shell surface of the innermost whorl. The range of hatchling diameter in all Cretaceous nautiloids (9-35 mm) is comparable to those of modern nautili (20-32 mm), although the Cretaceous nautiloids are characterized by a wider range with the smaller minimum diameter. The large hatchling size in Cretaceous nautiloids stands in marked contrast to those in ammonoids, which had much smaller hatchling size (mostly <2 mm in diameter) and became extinct at the end of the Cretaceous. Such distinct differences in reproductive strategy (i.e., hatchling and egg sizes) suggest that these differences may have played a significant role in the fate of ammonoids and nautiloids through the K/T mass extinction, as previously hypothesized by several paleontologists.  相似文献   

Mesofossil flora from the Late Cretaceous of New Zealand     

David J. Cantrill  Livia Wanntorp  Andrew N. Drinnan 《Cretaceous Research》2011,32(2):164-173

This study presents the first report of mesofossils of flowers, fruits and seeds found in the Cretaceous of New Zealand. The specimens were recovered from the Late Cretaceous (Maastrichtian, ca. 70 Ma) at Kai Point Mine, South Island in a sequence of floodplain sediments sampled just below the Barclay Coal Seam. Angiosperm flowers, fruits and seeds occur in the sample. The most common form is an actinomorphic flower with two whorls of three tepals. Anther bases are preserved and the ovary develops into a drupe, all features that are consistent with placement in the Lauraceae. Reproductive structures including seeds of conifers are also described, with some allied to the Podocarpaceae. This contrasts with interpretations of the flora based on macrofossils that indicate abundant Araucariaceae and highlights the different perspectives that mesofossil floras give to any assemblage. The results of the present study support a Late Cretaceous flora at this site mainly dominated by conifers with affinities to Podocarpaceae but also including lauraceous angiosperms.  相似文献   

新疆觉罗塔格小热泉子组火山岩的时代探讨   总被引：1，自引：1，他引：0  

肖伟峰  王宗秀  李海龙  鄢犀利 《岩石学报》2011,27(12):3615-3626

新疆东天山觉罗塔格地区广泛分布着石炭系-二叠系火山岩-沉积岩地层,小热泉子组是其中的一套以火山岩为主的地层.前人依据与之接触的底坎尔组中的中石炭世化石,将小热泉子组划为早石炭世.对觉罗塔格南部的小热泉子铜矿的研究,不同学者得出了差别较大的同位素年龄,而北部的小热泉子组目前还没有同位素年龄报道.我们对北部的底坎尔和干沟两地的小热泉子组火山岩进行了锆石SHRIMP测年,得到了271～275 Ma的年龄.这些测年数据与近几年其他学者的数据一致,表明早二叠世的岩浆活动比原来认为的更广,小热泉子组的时代应该属于早二叠世,其他地层单元的时代及其先后关系也需要重新认识.  相似文献   

福建锦城187Ma花岗岩的发现——对华南沿海早侏罗世构造演化的制约   总被引：7，自引：2，他引：5  

刘潜  于津海  苏斌  王勤  唐红峰  许海  崔翔 《岩石学报》2011,27(12):3575-3589

本文对福建沿海福清地区的锦城花岗岩和牛头尾花岗闪长岩进行了岩石地球化学、锆石U-Pb-Hf同位素分析.LA-ICP-MS锆石U-Pb定年结果显示锦城花岗岩的年龄为187±1Ma,为福建沿海首次发现的早侏罗世岩浆活动;牛头尾花岗岩形成时代为130±1Ma,代表燕山晚期(白垩纪)的一期岩浆活动.锦城花岗岩具有高5iO2、偏碱、高Fe2OT3等特征,为高钾钙碱性系列,岩石相对富集轻稀土,亏损Nb、Ta、Ti等高场强元素,富集Ba、Sr等大离子亲石元素,具高Rb/Sr( 1.31 ～ 1.93)比值及低Rb/Ba(0.26 ～0.29)、Eu/Eu*(0.30 ～0.56)、La/Yb(5.69 ～ 18.39),Sr/Y(2.24 ～2.29)比值,为典型的Ⅰ型花岗岩,且具有火山孤花岗岩的地球化学特征,很可能形成于与俯冲相关的构造背景.牛头尾花岗岩相比锦城花岗岩低SiO2,贫钾,而富镁、钙,属于花岗闪长岩.其更亏损Nb、Ta及富集Ba、Sr,具较低Rb/Sr(0.27)、Rb/Ba(0.09)比值和较高的Eu/Eu*(0.98)、La/Yb( 16.87),Sr/Y( 19.08)比值,同样为具有弧特征的钙碱性Ⅰ型花岗岩,也形成于与大洋俯冲有关的构造背景.锦城花岗岩和年头尾花岗闪长岩具有相似的锆石Hf同位素组成,εHf(t)分别为2.18～4.73和1.25 ～4.15,tDMC均为～ 1.0Ga,表明二者起源于相同的新元古代新生地壳.结合已有的资料,本次研究发现锦城花岗岩与南岭地区同时代岩浆岩( 194 ～ 172Ma)在成因上有密切的联系,暗示古太平洋板决的俯冲很可能自早侏罗世开始.这样,华南古特提斯构造域向古太平洋构造域的转换很可能发生在早侏罗世之前,大致在205 ～ 190Ma期间.  相似文献   

南阿尔金山清水泉镁铁-超镁铁质侵入体LA-ICP-MS 锆石U-Pb同位素定年及其意义   总被引：9，自引：1，他引：8       下载免费PDF全文

马中平李向民  徐学义孙吉明 唐 卓 杜 涛 《中国地质》2011,38(4):1071-1078

清水泉镁铁-超镁铁质层状侵入体位于南阿尔金山阿帕—茫崖构造带中-北部的清水泉地区,其北部与南阿尔金山超高压变质带紧邻。该岩体包含有3～4个由辉石橄榄岩-角闪辉长岩构成的岩浆旋回,与元古宙变质沉积岩系呈侵入接触关系。对其中的角闪辉长岩进行了LA-ICP-MS锆石U-Pb同位素测年,其206Pb/238U表面年龄为(461±2)Ma～(471±2)Ma,其加权平均值为(467.4±1.4)Ma(n=21,MSWD=2.5),所测锆石具有明显的岩浆振荡环带,Th/U比值为0.32～1.16(平均0.64)。测年结果显示,清水泉镁铁-超镁铁质岩体的形成时代晚于南阿尔金山超高压变质岩的峰期变质时代(504～487 Ma),而老于该地区A型花岗岩的时代(425 Ma左右)。分析认为,伴随着同时代的"双峰式"岩浆侵入作用及广泛的变质热事件,大约465 Ma时的南阿尔金山已经由前期的陆-陆碰撞造山阶段转入到了碰撞后的裂谷伸展作用阶段。  相似文献   

川东北地区长兴组生物礁成礁类型及分布   总被引：3，自引：1，他引：2       下载免费PDF全文

刘治成张廷山  党录瑞郑 超 董银磊 杨 巍 《中国地质》2011,38(5):1298-1311

目前在川东北地区发现了龙岗、普光、黄龙、五百梯等多个生物礁气藏,它们具有储层较厚、面积较大、储量丰度高等特点,展示出了广阔的滚动勘探开发前景。本文根据野外露头与钻井资料,结合前人研究成果,通过对生物礁的造礁生物古生态特征研究,按照生物礁所处的古地理位置、礁体的形态和礁岩的特征,归纳总结出川东北地区长兴组生物礁主要分为台地边缘礁和台内点礁,其特征差异明显。台地边缘礁主要表现为规模较大,礁组合相带完整,礁体旋回较少,水体能量强,其分布受古地理位置、古地貌环境控制,主要沿海槽两侧呈串珠状分布;台内点礁主要表现为规模较小,水体能量较弱,造礁生物个体较小,无礁前礁后沉积,礁体旋回较多,发育有凝块石,主要发育在长兴组中下部,分布规律性不强,主要受古地貌影响,沿台内局部高地随机分布。  相似文献   

西藏冈底斯带中南部与俯冲有关的早侏罗世花岗闪长岩:锆石U-Pb年代学及地球化学证据   总被引：1，自引：0，他引：1  

陈炜  马昌前  宋志强  龙桃成  夏天齐  蔡立元  王彤 《地质科技情报》2011,30(6):1-12

肖打松多花岗闪长岩位于西藏冈底斯花岗岩带中段以南,主要岩石类型有:细中粒黑云母(角闪石)花岗闪长岩、细中粒含斑黑云母(角闪石)花岗闪长岩、细中粒斑状黑云母(角闪石)花岗闪长岩,岩石具钙碱性特征,w(SiO2)=61.58％～72.16％,w(K2O)/w(Na2O) =0.64～1.15,相对富钠,A/CNK=1.25...  相似文献